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UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 890 

Contribution from the Bureau of Animal Industry 
JOHN R. MOHLER. Chief 



Washington, D. C. 



October 7, 1920 



MILK-PLANT EQUIPMENT 

By 

ERNEST KELLY, in charge of Market Milk Investigations, and 
CLARENCE E. CLEMENT, Market Milk Specialist, Dairy Division 



CONTENTS 



Page 

Selection of Equipment 1 

Equipment Required 3 

Scales and Weigh Can 4 

Drip Saver 5 

Receiving Vat and Storage Tanks . . 6. 

Clarifler 7 

Pasteurization 7 

Selection of Pasteurizing Equipment . 8 

Heaters . 10 

Holders 16 

Coolers 18 

In-the-Bottle Pasteurization .... 20 

Systems of Pasteurizing Used ... 22 

Temperature Regulator 23 



Pasteurization — continued . 

Recording Thermometer . . . ^ . . 23 

Bottle Fillers and Cappers 25 

Bottle Washers 29 

Can Washers 31 

Labor-Saving Devices < 32 

Power Plant 33 

Steam or Electric Power 34 

Artificial Refrigeration 34 

Use of Exhaust Steam 37 

Cost of Plailt Equipment 38 

Lists of Equipment Required for Various- 
Sized Plants 38 




WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1920 



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OCT 21 f929 






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UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 890 




yu^ ^w<^ 



Contribution from the Bureau of Animal Industry 
JOHN R. MOHLER. Chief 




■^^*^^U 



Washington, D. C. 



October 7, 1920 



MILK-PLANT EQUIPMENT. 

By Ernest Kelly, in charfic of Market Milk InvestiffatioiiK, sind Clarence E 
Clement, Market Milk Specialist, Dairy Dirision. 



CONTENTS. 



Page. 

Selection of equipment 1 

Equipment required 3 

Scales and weigh can 4 

Drip saver : 5 

Receiving vat and storage tanks 6 

Clarifier 7 

Pasteurization 7 

Selection of pasteurizing equip- 
ment 8 

Heaters 10 

Holders 16 

Coolers 18 

In-the-bottle pasteurization 20 

Systems of pasteurizing used__ 22 



Page. 



Pasteurization — Continued. 

Temperature regulator 23 

Recording thermometer 23 

Bottle fillers and cappers 25 

Bottle washers 29 

Can washers 31 

Labor-saving devices 32 

Power plant 33 

Steam or electric power 34 

Artificial refrigeration 34 

Use of exhaust steam 37 

Cost of plant equipment 38 

Lists of equipment required fur vari- 
ous-sized plants 38 



SELECTION OF EQUIPMENT. 

Great care must be given to the selection of milk-plant equipment. 
Man}'' mistakes have been made through the selection of too much 
machinery or machinery which was too complicated. In other cases 
it has often been found after the equipment has been put in opera- 
tion that the capacity of different machines was either too great or 
too small. Such mistakes in selecting equipment are usually detected 
when it is too late, and it would be advisable, therefore, to consider 
seriously the following points before buying the equipment for a 
milk plant: 

1. Simplicity. — The simpler the machine the better. Unnecessary 
parts make the machine difficult to operate and to clean and more 
liable to get out of order. 

2. Ease of cleaning. — Unless the machine can be cleaned easily the 
labor of cleaning will be greater, and the work may be neglected. 
There should be a minimum of parts and joints not easily accessible. 



2 BULLETIN 890, U. S. DEPARTMENT OE AGRICULTURE. 

3. Ease of sterilizing. — Some types of machinery are much easier 
to get at for steaming than others. All apparatus in which milk is 
handled must be sterilized daily with live steam ; hence the item of 
" inaccessibility " should not be overlooked. 

4. Initial cost. — Machinery should not be purchased on the basis 
of cheapness alone; it is often economy to purchase some of the 
highest-priced machines. The initial cost, however, must be con- 
sidered and weighed against all other factors. 

5. Rapidity., ease., and economy of operation. — A study of the 
machinery in actual operation is necessary to determine these factors. 

6. Avoidance of ruhher gashets and, fittings. — All fittings in milk- 
handling equipment, so far as possible, should be of metal. 

7. Proper capacity. — The equipment purchased should be of suffi- 
cient size to handle all probable increase of business; but it should be 
borne in mind that plant equipment depreciates rapidly, and it is 
not advisable to procure oversize apparatus which will not last until 
the anticipated increase has taken place. 

8. Duraljilitij. — Cheap machinery often wears out or gets out of 
order in a very short time. It is more economical to purchase a well- 
constructed and durable machine even if the initial cost is somewhat 
higher. 

The life of milk-plant equipment and machinery will depend upon 
the original condition, amount of use, and the care given it. As a 
rule such equipment receives hard and constant usage and depreciates 
quite rapidly. The average annual depreciation of all milk-plant 
equipment in 60 plants varied from 4 to 33i per cent, with an average 
of 14.6 per cent. The annual per cent of depreciation of the various 
items of equipment in 20 other plants was as follows : 

Tablk 1. — Dcprcciittid)! of rarioiis itciii>i of (■qHii)iii<iif in ,iO [ildiils. 



Type of machinery. 



Bottle fillers and cappers 

Bottle washers 

Pasteurizers 

Power-plant equipment 

Cans 

At 12 of these 20 plants the depreciation was 20 per cent on fillers 
and cappers, bottle washers, and pasteurizers, while at 8 of them the 
depreciation on power-plant equipment was 10 per cent, these figures 
being the most common. 

It may be safely estimated that at the average plant the milk- 
handling equipment depreciates nearly 20 per cent, or, in other 




MILK-PLAISTT EQUIPMENT. 3 

words, its average life is about five 3^ears. At many plants the life 
of the equipment is much longer, however, often exceeding 10 years, 
due largely to better machinery and to the good care that it receives. 
The low average life in a great measure is due to the fact that after 
a few 3^ears the machinery becomes obsolete and has to give way to 
modern equipment. In the case of cans these figures do not neces- 
sarily indicate that a can will wear out in five years; much of the 
depreciation is due to lost cans. 

EQUIPMENT REQUIRED. 

In general, the following equipment is required for the ordinary 
city milk plant : 

1. Weigh can. with platform scales. 

2. Drip saver. 

3. Receiving vat or jacketed, glass-lined storage tanks. 
•4. Clarifier or Alter. 

5. Pasteurizer. 

6. Holder. 

7. Cooler. 

8. Temperature regulators and recorders. 

9. Supply tank to the filler. 

10. Fillers and cappers. 

11. Bottle washer. 




Fig. 1. — Dump or weigh can with platform scales. Tank sunk in floor to make dumping 

of milk easier. 



4 BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 

12. Can washer. 

13. Ijiibor-saving devices, as elevators and conveyers. 

14. Boilers, engines, refrigeration machinery, motors, hot-water heater, etc. 

15. Sanitary milk pumps and piping. 

16. Separator and churn. 

17. Cans, bottles, cases, etc. 

SCALES AND WEIGH CAN. 

At very small plants the milk can be weighed in the cans and the 
weigh tanks will not be needed. In all cases, whether milk is paid 
for by the gallon or by weight, it should be weighed. If milk is 
paid for by the gallon the weight can be readily converted to gal- 
lons ; in fact, there are scales on the market which record the quantity 
in gallons as well as pounds. One company handling a little more 
than 4,000 gallons of milk daily decided after several years to buy 
and sell the milk by weight. Scales were installed and the difference 
between the measure by the cans and the actual quantity of milk 
received, as shown by the scales, was determined. Table 2 shows the 
differences in a two-month test. 



Table 2. 



-Difference heticeen can measure and actual quantity of milk received 
as shown hy scales, at a city plant. 





Items. 




First 
month. 


Second 
month. 




Gallons. 
126,460 
124,331 


Gallons. 
138, 485 


Scale - 


135,941 












2,128 


2,544 


• 





Thus, during April there Avas a difference of 2.128 gallons and in 
May 2,544 gallons. At this rate the plant paid for over 2,000 gallons 
of milk more than it actuall}^ received in each of the two months, or 
a difference of more than $600 a month, if milk is worth 30 cents a 
gallon. 

At another plant, where the milk was received by measure, 55 
10-gallon cans of milk were weighed, first weighing the full can 
and then weighing the empty can after it had drained on a drip pan. 
The lowest net weight for the can of milk was 80 pounds and the 
highest 85| pounds, or a variation of 5f pounds. The average of the 
55 cans was 884 pounds, or 2| pounds less than the usually accepted 
weight for 10 gallons of milk. Only full cans were included, so the 
dealer actually lost 3.19 per cent. This dealer handled 2,000 gallons 
daily, and valuing the milk at 30 cents a gallon the daily discrepancy 
would be 63.8 gallons, or an overpayment of $19.14. The purchase 



MILK-PLANT EQUIPMENT. 5 

of a set of scales would provide for an equitable method of pur- 
chasing milk, whereby farmers would receive full payment for the 
exact quantity of milk delivered. 

Losses of milk which result from buying by measure instead of 
by weight are due to the following causes: 

1. Cans not filled by farmer. 

2. Milk slopped in transit. 

3. Cans dented and not holding full quantity. 

4. Leaky cans. 

5. Loss from contraction and expansion of milk. (Experiments have 

shown that milk shrinks at least 0.2 per cent in cooling from 70° 
to 50° F.) 

DRIP SAVER. 

A drip saver (fig. 2) helps to reduce the loss from shrinkage of 
milk. This may be a homemade affair or one can be purchased at a 
moderate price from a dairy-supply company. 




Fig. 2. — Method of drainins 



cans to prevent waste. The illustration shows also jacket- 
ing of cans to keep milk cool. 



6 



BULLETIN 890, U. S. DEPAKTMENT OF AGRICULTURE. 



The following table shows the quantities of milk saved by drip 
savers at several plants : 

Table 8. — Quantity of milk, saved by drip savers at several plants. 



Plant No. 


Quantity 
of milk 
dumped. 


Milk saved wth a 
drip saver. 


1.. 


Gallons. 
6,000 
4,000 
3,000 
2,000 


Gallons. 

16 

15 

12 

6 


Per cent. 
0.266 


2 . , 


.375 


3 


.40 


4 


.30 







Losses of milk from handling in city milk plants as reported by 
115 dealers varied from 0.3 per cent to 7 per cent, and the average 
was 2.29 per cent. If a dealer handles 3,000 gallons daily, with a 
shrinkage of 2.29 per cent, his daily loss would be 68.7 gallons, or 
at 30 cents a gallon, $20.61, or $7,522.65 a year. Such a loss is a 
big item and every precaution should be taken to keep down the 
shrinkage. 

There is necessarily a certain amount of shrinkage in transferring 
milk from cans to bottles and in the process of clarifying and 
pasteurizing. Special attention to this matter, however, has been 
given by some plants and the losses considerably reduced. Collecting 
pans should be placed under all milk apparatus where milk is apt to 
spill, and especially under the filling machines, to catch all drip. While 
the milk saved should not go back to the filler, it may be utilized in 
other ways. 

RECEIVING VAT AND STORAGE TANKS. 

Jacketed storage tanks or a receiving vat are used to hold the milk 
from the time it is received and dumped until it goes to the pasteur- 
izer. The storage tanks are insulated and are often fitted with 
jackets so that the milk can be kept cold by means of brine. (See 
fig, 3.) The milk is agitated by air blown in from the bottom or 
by a revolving paddle. These tanks are valuable where milk is to be 
lield for a considerable time before it is pasteurized. At many plants 
milk is held in these tanks for several hours and a great saving in 
milk cans, refrigeration, labor, and floor space is effected. 

If the milk is not held over for any considerable time it can be 
held in an ordinary receiving vat which may have revolving coils 
containing the cooling medium that keeps the milk cool and agitated. 
A larger receiving vat will be required if the continuous system of 
pasteurization is used than if the vat system is employed, as in the 
latter case the milk may go direct to the pasteurizing vats. 



MILK-PLANT EQUIPMENT. 



CLARIFIER, 



The clarifier (fig. 4) is a centrifugal machine used to remove visi- 
ble dirt from the milk. There are on the market several clarifiers 
that do very efficient work. 

PASTEURIZATION. 

Pasteurization is quite generally recognized as necessary unless milk 
has been produced and handled under special conditions that make 
its use safe in the raw state. The proper pasteurization of milk con- 
sists in heating it to 145° F., and holding it at that temperature for 
30 minutes, A variation of 2° F. above or below is allowable. All 
disease-producing bacteria w^hich may occur in milk are destroyed 
by proper pasteurization, and a considerable quantity of other bac- 
teria are also destroyed, so that, provided the milk is properly taken 
care of after pasteurization, its keeping quality will be improved.^ 

Formerly milk was pasteurized to a large extent by the " flash " 
system. By this system the milk is heated to 155° F. or higher and 
then cooled. Exhaustive laboratory investigations, as well as actual 




Pig. 3. — Milk-storage tanks used in large plants to store milk at low temperature before 

it is pasteurized. 

practice on a commercial scale, have shown that this system is not 
satisfactory, and that positive holding is necessary. 

1 For detailed information on pasteurization see Bureau of Animal Industry Circular 
184, Bureau of Animal Industry Bulletin Ifil, and Department Bulletin 342. 



8 BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 




Fig. 4. — Battery o£ clariflers used at a large plant. 



SELECTION OF PASTEURIZING EQUIPMENT. 

A large number of different types and styles of pasteurizers are 
on the market, and one should know what requirements are to be 
fulfilled before attempting to select a machine. 

In general the type of pasteurizer selected should be adapted to the 
particular plant for which it is intended. A small plant will often 
require a different type of machine from a large one. A plant han- 
dling milk only may require a type different from that required by 
one handling by-products also. 

Other questions which have a bearing on the selection of a pas- 
teurizer are : Is the daily output constant ? Is the business increasing 
or constant? The large dealer must have a machine that will handle 
a large volume of milk in a short time. 

Among the points to be considered in the selection of a pasteurizer 
are the following: 

1. Simplicity of the machine. 

2. Ease of cleaning. 

3. Ease of sterilizing. 

4. Economy of operation. 

.5. Avoidance of high temperatures in the heating medium by liaving 

a large heating area. 
6. Accuracy of holding. 



MILK-PLAXT EQUIPMEN-T. 9 

7. Initial cost. 

8. Durability. 

9. Avoidance of chance of forcing; the milk through at too liiglr a speed. 

10. Ease and rapidity of operation. 

11. Elimination of milk pumps, whenever practicable. 

12. Adaptal)ility to increased capacity, by installing a(hlitional units. 

13. Minimum of ininecessary agitation of milk. 

14. Floor spac-e re<]uired. 

15. Minimizing human element in operation. 

16. Heating all of the milk uniformly. 

A pasteurizer Avith parts not easily accessible will require extra 
time to keep it clean and should be avoided. It is important that 
the pasteurizer have a large heating area, so that the temperature of 
the heating medium need not be much higher than the temperature 
to which the milk is to be heated. This will avoid the danger of 
heating some parts of the milk to too high a temperature, which 
gives it a scorched or burned taste and maj' also injure the cream line. 

To be on the safe side the temperature of the heating medium 
should not be more than 10° or 15° F. above that to which the milk 
is to be heated. As a heating medium water gives good results and 
its temperature should be under control at all times. Steam should 
not be used direct as a heating medium in most types of pasteurizers. 

Bv applying the so-called "regenerative" principle to the heating 
and cooling media many plants are able to cut down the amount of 
heat and refrigeration required. This principle may be applied by 
either the " milk regenerative " or the " water regenerative " system. 
With the milk regenerative system the cold milk coming into the 
pasteurizer passes through the first section of the cooling tubes over 
which the hot milk from the holder flows. In this way the incoming 
milk is partly heated, often to between 110° and 120° F. before it 
goes to the heater proper, while the milk going over the cooler is 
cooled by the incoming milk inside the tubes to 60° or 70° F. before 
it reaches the tubes containing the cooling water. 

With the water regenerative system the water from the first section 
of the cooler, having been heated to within a few degrees of the hot 
milk, needs to have only a few heat units added to it before it goes to 
the heater to heat the incoming milk. The water from the heater 
in turn having been cooled by the incoming milk goes to the cooler, 
where it is used for cooling the hot milk. The water regenerative 
system is the most desirable, as much cleaning ai milk pipes is neces- 
sary with the milk regenerative system. Temperatures obtained with 
regenerative systems of pasteurizing are shown in Table 4. 

At many plants the milk is preheated by means of this regenerative 
principle to about 85° or 90° F. before it goes to the clarifier. At 
that temperature clarification is more efficient and less foam is pro- 
lS0f)O8°— 20— Bull. S90 2 



10 



BULLETIN 890, U. S. DEPAETMP^NT OF AGRICULTURE. 



duced. Preheating also renders the pasteurization more nearly uni- 
form, as the milk goes to the machine at a fairly constant temperature. 

Table 4. — Temperatures of nvilk at pasteurizing plants that use reijenerative 

systems. 







Tem- 






Tem- 








perature 






perature 






Tem- 
perature 
of milk 

as 
received. 


after pre- 




Tem- 


after pre- 






heating 


degrees 


perature 


cooling 


Degrees 


Plant No. 


by 
regen- 


heated 
by hot 


of milk 
coming 


by 
regen- 


cooled 
by cold 




erator, 


milk. 


from 


erator, 


raw milk. 




before 




holder. 


before 








going to 






going to 








heater. 






cooler. 




' 


° F. 


° F. 


° F. 


° F. 


° F. 


° F. 


1 


40 
36 
34 

40 
39 

45 
40 
42 
40 


120 
116 
114 
120 
116 
120 
110 
108 
65 


80 
80 
80 
80 
77 
75 
70 
66 
25 


144 
144 
145 
145 
141 
144 
144 
142 
145 


50 
61 
52 
60 
66 
60 
65 
66 
60 


94 


2 


83 


3 


93 


4 


85 


5 


75 


6 


84 


7 


79 


8 


76 


9 


85 








30 


109 


70 


144 


60 


84 







Note. — The milk ngenorativo t.ystcni described in a previous paragraph was used in 
these plants. 

For a complete system of proper pasteurization the following 
equipment must be obtained : 

1. Heater. 

2. Holder. 

3. Cooler. 

In some cases the same apparatus may be used for all three proc- 
esses. 

HEATERS. 

In general, there are two types of heaters, the batch system heater 
and the continuous-flow heater. 



BATCH HEATERS. 



In the batch system the milk is heated in a A^at, on the inside of 
which is a coil through which the heating medium, usually hot water, 
is forced. This coil revolves slowly and gently agitates the milk. 
The hot water is either pumped through the coil or forced through 
by air and by the revolving of the coil. 

Another type of batch heater consists of a jacketed tank or vat 
in which the milk is agitated by a mechanical contrivance. Heat is 
supplied by steam or hot water in the outer jacket. Some of the 
older types of vats are provided with disks instead of coils, but 
they are much less satisfactory and are more likely to get out of 
order. It takes from 15 to 30 minutes to heat the milk in the vat 
and after it has reached the desired temperature (145° F.) it is held 



MILK-PLANT EQUIPMENT. 



11 



in the same vat for 30 minutes. The vat should be well insulated to 
prevent loss of heat during the holding process. The coils are some- 
times allowed to revolve during the holding process so that the cream 
will not rise and the milk will be held at a more uniform temperature. 

One of the dangers of the vat system is that the milk may be 
started out of the vat before it has been held for 30 minutes. At one 
plant it was noted that the milk was started out of the vat 11 minutes 
after it was brought up to 145° F, It was then allowed to go over 
a tubular cooler. The cooling process took about 35 minutes, so that 
while the last of the milk was held for 45 minutes the first part was 
held for only 11 minutes. 

Milk may be cooled in the vat by forcing cold water and brine 
through the coils, or by water jackets, or it may be run over a separate 
cooler. Where it is cooled in the vat the process is very slow, and the 
milk will not show a clear cream line so readily as when cooled 
quickly over a separate cooler. Cooling in the vat also may cause 
leaks in the coils, due to the repeated sudden changes in temperature. 
A continuous system may be obtained with the batch system of 
pasteurization by using a battery of three or more vats. While the 
third vat is being filled and heated the milk in the second vat is 
being held and that in the first vat is being drawn off to the cooler. 
The time required to empty the vat depends somewhat on the capacity 
of the cooler, so it is important that the cooler be of ample capacity. 
The capacity of the vats may be increased by preheating the milk 
by some form of heater before it enters the vats. If the milk is 
slightly cooled in the vats before it is allowed to go to the cooler the 
time the milk is held at 145° F. will be made uniform for all the milk 




Fig. 5.— Pasteurizing milk by the batch or vat system. 



12 BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 

and the capacity of the outfit will be increased. Another advantage 
of precooling is that the records will show the exact time the milk 
was held at 145° F. if a recording thermometer is used. 

The covers of this type of heater should be kept closed ; otherwise 
there may be a considerable loss from evaporation and the milk may 
be contaminated. It is important with the vat system that the coils 
revolve at the proper speed. If they are allowed to run too fast the 
milk will be unduly agitated and injury to the cream line may result. 
The ordinary 300-gallon vat should be run at 45 revolutions a minute. 

Some of the advantages of vat heaters are : 

1. Simplicity. The apparatus is very simple. 

2. Easily operated. 

3. The vats are durable and comparatively inexpensive. One vat may 
serve for heating:, holding, and cooling, though the last is not usually advis- 
able, as previously mentioned. 

4. For small plants the vats are economical, on account of the many uses 
to which they may be put. Besides serving as heater, holder, and cooler, 
the vat also may serve as a dump tank and storage tank for the milk. 
The milk may be placed in the vat when received and be held in the vat at 
the desired temperature until ready for pasteurization. Where a whole- 
sale business is conducted, the milk may be held in the vats at low tem- 
perature after it is pasteurized and cooled until the cans are filled and sent 
out to the wholesale trade. 

5. The time of holding can be positive if operated properly. 

6. During the holding process the milk comes into contact with no new 
surfaces between the completion of the heating process and the time the 
milk is cooled ; thus there is less chance for contamination and less appa- 
ratus to clean. 

7. The capacity of the plant may be readily increased by adding another 
unit. (A small plant may get along with one vat for a while, and as the 
business increases additional vats may be added and a continuous system 
established.) 

Some of the disadvantages of the vat system are : 

1. Some operators have difficulty in obtaining a good cream line with 
this system. 

2. A comparatively long time is required to heat the milk. 

3. It is not automatic. The attendant must spend a considerable por- 
tion of his time operating the valves for filling and emptying the vats. 

4. With some types of vats the bearings or stuffing boxes of the coils, 
unless properly taken care of, may come into contact with the milk, and 
leaks m-ay cause considerable trouble. 

5. All milk is not held at the pasteurizing temperature the same length 
of time. Some of the milk may be held more than 30 minutes, and thus 
the cream line may not be so clear. If the milk is precooled a few degrees 
in the vat before going to the cooler this disadvantage may be eliminated. 

fONTINTIOITS-FI.OW TIKATKRS. 

The most common continuous-flow heaters may in general be 
classified into three types, which have sometimes been designated as 



MILK-PLANT EQUIPMENT. 



13 



the " kettle " or " Danish " heater, the " drum " or " film " heater, 
and the " internal tubular '■ heater. 

'Kettle or Danish heater. — The kettle or Danish heater (fig. 6) 
consists of a kettlelike receptacle in which the milk is heated by a 
water jacket surrounding it. Into this jacket steam is introduced 
in order to bring the contents to the desired temperature. The milk 
enters the inside of the apparatus at a point near the bottom and is 
forced out at the top by means of revolving paddles. These paddles 
may force the milk upward for 5 to 10 feet, and thus the machine 
acts as a pump. The heating surface is comparatively small, and it 
is therefore necessary to use a high temperature in the heating 
medium. For this reason it is very difficult to get a uniform tempera- 
ture for all portions of milk going through this heater. 

This tygQ of heater is often used where milk is heated and not held 
for any length of time ; but it may also be used with nearly any type 
of holder. The system of heating milk to high temperatures for short 
periods is known as the '' flash "*' process of pasteurization. This 
system is not desirable, but the heating units are satisfactory if used 
in connection with a holding device. 

The principal advantages of this type of heater are; 

1. luexpensiveness. 

2. Small floor space required. 

3. It is economical and easy to operate. 

4. It is quite easily cleaned. 

5. It may act as a pump to elevate the milk to the holder. 

The principal disadvantage of this type of heater is the difficulty 
of maintaining a uniform temperature. The area of the heating 




Fk;. tj. — Pasteurizer or the Danish or " iiettle " type, with retarder. 



14 BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 

surface is so small that the heating medium must be of a considerably 
higher temperature than that to which the milk is to be heated, and 
steam is introduced directly into the heating chamber. As the heating 
medium is sometimes allowed to run as high as from 190° to 200° F., 
certain parts of the milk may be overheated, which gives a scorched 
or burnt taste to the milk. An automatic temperature control is very 
essential with this type of heater. The flow of the milk to the ma- 
chine, as well as its temperature, will fluctuate more or less, and unless 
there is an accurate automatic temperature control attached there is 
almost sure to be an unevenness of temperature in the milk as it comes 
from the heater, even though a man spends his entire time in operat- 
ing the machine. For example, at a plant using this type of heater 
with no temperature control, temperatures were taken in each com- 
partment of a positive holder of the milk as it came from the heater 
and these temperatures varied from 144° to 156° F. 

Good results are obtained by using a preheater or a regenerator in 
conjunction with this type of heater. In this way the capacity of the 
heater is increased, thus lessening the tax on the machine, and less 
extreme temperatures can be used. At some plants using this system 
of pasteurization the milk is preheated to from 110° to 120° F. before 
it enters the pasteurizer proper ; thus the milk has to be heated only 
25 or 30 degrees more in the machine. Much more satisfactory and 
uniform results are obtained in this way. Temperatures obtained 
with this preheating system are shown in Table 4, plant No. 7. 

A combination of this type of heater and a series of vats will pro- 
duce good results. The milk can be heated to. 120° or 135° F. before 
it goes to the vats, and thus the dangers of overheating can be 
eliminated. The remainder of the heating will be accomplished in 
the vats, and the milk will be held in them until it is to be cooled. 

Drum or film heater. — With some machines of the drum or film 
type (fig. 7) the milk flows between two or more heating surfaces in a 
thin film, while in others it flows in a thin film over a revolving drum 
inside of which is the heating medium. The heating water is kept 
at the desired temperature either by heating it in a tank outside the 
machine or by the introduction of steam directly into the machine. 
The former method is preferable, as there is less chance of overheat- 
ing the milk. The milk must be kept in motion, and this is usually 
done by means of a revolving drum. The regenerative principle is 
used with some machines of this type. 

Some of the advantages of this type of heater are : 

1. The area of the heating surface is considerably greater than with 
the " Icettle " type, and there is less danger of overheating some of the milk. 

2. It is less expensive than some other types of heaters. 

3. The machines are durable. 



MILK-PLANT EQUIPMENT. 



15 



Some of the disadvantages are : 



1. Some of the heaters contain several parts and are difficult to clean and 
to keep in good running condition. 

2. They are not especially adapted to increase in capacity by adding 
additional xniits. 

Internal tubular heaters. — With the internal tubular type of heater 
(fig. 8) the milk passes through a tube inclosed within another tube or 
in a jacket containing the heating medium. In some of them the outer 
pipe or jacket is insulated to prevent loss of heat by radiation. The 
milk flows in an opposite direction to that of the heating medium, 
and in this way the heat units of the heating medium are economi- 
cally utilized and the milk is heated without any extreme fluctuations 
of temperature. The heating medium is hot water, which is heated 
by the introduction of steam before it enters the coil. As this heating 
water can be forced through rather rapidly and the area of the 
heating surface is comparatively large, the temperature of the heat- 
ing medium need not be much higher at any time than that to which 
the milk is to be heated. 

Some of the advantages of this type of heater are : 

1. Simplicity. 

2. Some tyjpes are comparatively inexpensive. 

3. Some types are adaptable to increase in capacity by adding additional 
units. 

4. Durability. There are few parts to get out of repair. 

5. Regenerative principle of heating can be utilized, permitting economy 
of heat and refrigeration. 




Fig. 7. — Continuous pasteurizer of the film or drum type. Clarifier on right. 



16 



BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 




Fk;. S. — Pasteurizer and cooler of the internal-tuhe type. 

6. Easy sterilization. If the ends of the tubes are closed steam can be 
introduced under pressure and the apparatus thoroughly sterilized. 

7. High temperatures of the heating medium not necessary. 

Some of the disadvantages of internal tube heaters are : 

1. A large quantity of piping to be cleaned. 

2. The milk may be agitated considerably by passing from one pipe to 
another. 

3. Some forms are quite expensive. 

4. Some types are not adapted to increase in capacity by adding addi- 
• tional units. 

It is very important that pumps supplying milk to heaters of this 
type are not run too fast and that a uniform quantity of milk is 
allowed to flow to the pump. All machines should have automatic 
temperature controls for maintaining a uniform temperature. 

HOLDERS. 

After the milk is heated to the desired temperature (145° F.) it 
must be held at that temperature for 30 minutes. The process of 
holding is usually carried on in an apparatus separate from the 
heater or cooler. 

In general, there are two types of holders, the positive holder and 
the continuous holder or retarder. 



MILK-PLANT EQUIPMENT. 



17 



Positive holders. — By positive holding is meant that the milk, after 
being heated to the desired temperature, remains in a certain com- 
partment a definite length of time and is then cooled. Usually the 
milk is drawn from the compartment and cooled over a separate 
cooler. Generally the filling and emptying of the compartments of 
the holder are controlled automatically (fig. 9), but in the case of the 
batch system, where the vat is used as a holder, the valves are con- 
trolled by hand and it is necessary for the attendant to open and 
close them at the proper time. Some compartment holders also are 
controlled by hand valves. Holders should be so insulated that little 
heat is lost while the milk is being held, and with positive holders of 
the automatic type it is very essential for the valves to be accurate. 
The valve of the compartment to be filled should always be closed 
tight before the milk begins to flow in; otherwise some of the milk 
will pass through without being held. With any holder it is im- 
portant that all pipes or " pockets " in which the milk is held during 
the heating or holding processes be well insulated, so that the holding 
temperature can be maintained. 

Continuous holders. — With continuous holders or retarders the 
milk passes through the apparatus in a continuous flow. This flow 




1 1 1,. 9. — Automatic holding device for the pasteurization of milk. 
186608°— 20— Bull. 890 ^3 



18 



BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 




Fk;. 10. — Open or siirf;ice milk cooler. 

of milk is retarded in its course by some form of obstruction, such as 
baffle plates, or in some types it passes through a series of winding 
pipes. It is supposed to take half an hour for the milk to pass 
through the holder. Some continuous holders consist of a series of 
two or more tanks, the milk flowing from one tank as soon as it is 
full to the next, and half an hour is required for it to go through 
all the tanks. 

Good results have been obtained with many holders of the con- 
tinuous type. The danger with such holders, however, is that some 
particles of the milk may not be held so long as others and that the 
milk may be forced through the apparatus and none of it held the 
proj)er length of time. Tests made on several retarders of one type 
have shoAvn that some of the milk was held only 10 minutes. Tests 
should be made on all such apparatus to ascertain whether the milk 
is being properly held, and retarders that do not do accurate work 
should not be used. 

Of 237 plants surveyed in the year 1916, 15 were using the " flash " 
system, 24 were using " retarding '' systems, and 198 were using 
positive holders. 

COOLERS. 

In general there are two common types of coolers — the open- 
surface tubular cooler and the internal-tubular cooler. With the 
open-surface cooler the milk passes over the tubes in a thin film. 
The cooling medium passes through these tubes on the inside. There 
is usually water in the first sections and brine or direct-expansion 



MILK-PLANT EQUIPMENT. 19 

ammonia in the remaining sections. Where the regenerative system 
of pasteurization is used the cool milk is often allowed to pass 
through the inside of the first sections of the cooler. With the 
open-surface cooler the milk is exposed to the air in the room, and 
for that reason the air should be kept pure. It is important that 
the cooler be of sufficient capacity to cool the required quantity of 
milk. When the cooler is not large enough there is a tendency for 
the operator to allow the milk to go over the cooler too fast for 
proper cooling. 

The internal-tubular coolers are constructed on the same prin- 
ciple as the internal-tube heaters; that is, the milk passes through 
a pipe which is itself inclosed in a pipe or jacket containing the cool- 
ing medium. The length of tubing required in cooling coils is about 
double that of heating coils. With this type of cooler the milk does 
not come into contact with the air at any time. A claim made for 
the open cooler is that the milk is aerated, while with the internal- 
tube cooler bad odors have no chance to escape. On a commercial 
scale, however, little trouble has been found from this source. There 
is no loss of milk from evaporation with the internal-tube cooler, 
while there may be considerable loss from this source with the open 
cooler, especially if the cooler is in a draft. 

If the open cooler is covered, contamination from the air will be 
reduced ; however, it is more desirable to have pure air in the room 
where the cooler is located, as it requires considerable care to keep 
these covers clean, and they are often clumsy to handle. If covers 
are used, the sterilization of the cooler is made easier. 

It is much easier to sterilize the internal-tube cooler than the open- 
surface cooler. If steam is introduced into the internal cooler and 
the apparatus closed, it can be thoroughly sterilized. One way to 
sterilize the surface cooler is to admit steam to the inside of the 
tubes and at the same time run hot water over the outside of the 
cooler. The hot water will be vaporized and quite thorough sterili- 
zation will result. Another method which is perhaps more satisfac- 
tory is to close the covers tightly over the cooler and introduce live 
steam. 

In some forms of regenerative pasteurization the incoming milk 
will pass through the first few tubes of the cooler. This saves steam, 
but the tubes are difficult to clean. 

The open-surface coolers should be so constructed that water can 
be used in the top sections and brine or direct-expansion ammonia 
in the bottom sections. The capacity should be great enough to cool 
the milk as fast as it comes from the holder. The tubes should not 
be too long in comparison with their height. When the tubes are 
too long their whole length sometimes is not covered by the milk, and 
refrigeration is wasted. In some cases, however, it is necessary to 



20 



BULLETIN 890, U. S. DEPARTMENT OF AGRICITLTUEE. 




Fig. 11. — In-the-bottle pasteurizer, sbowiug pumps which force the sprays of hot water 

over the bottles. 

have the cooler considerably longer than it is high, so that the avail- 
able elevation will allow gravity flow of the milk. Table 7 shows 
the methods of cooling used at various plants. Sometimes coolers 
are made in three sections, water being used in two of them and 
brine or direct expansion in the third. In this way better use of 
the water is made. At one plant the temperature of the milk from 
the first water section was 78° F,, from the second 64° F., and from 
the brine coil 34° F. The second section cooled the milk from 78° 
to 64° F., thus saving considerable refrigeration. (See fig. 8 for 
internal cooler.) 

IN-THE-BOTTLE PASTEURIZATION. 

With the " in-the-bottle " system of pasteurizing, which has been 
developed within recent years, the milk is pasteurized after it has 
been put into the bottles. The bottles of milk, in cases, are placed 
in a compartment and heated to the desired temperature, held, and 
cooled. With some types the milk is heated, held, and cooled in the 
same compartment, while in others the bottles, after being removed 
from the cases, pass slowly through the machine, being heated at 
the beginning and cooled at the end of the process. With this system 
it takes 30 minutes for the bottles to travel from the point where they 



MILK-PLANT EQUIPMENT. 



21 



have been heated to the desired temperature to the point where cool- 
ing is begun. The heating with the in-the-bottle pasteurizer is 
usually accomplished by passing sprays of hot water over the bottles. 
(See figs. 11 and 12.) Either a special cap is used on the bottle 
or the bottles are covered with a specially constructed pan. In the 
latter case the hot water usually flows through small holes in this 
pan and forms a thin film around the bottles. Where the special 
cap is used the pans are not required. The cooling is accomplished 
by changing from hot water to cold. After the milk is heated, held, 
and cooled it may remain, in some types, in the machine and be kept 
at a low temperature until time for delivery. With some types of the 
in-the-bottle pasteurizer the milk in the bottles is heated by live 
steam and the cooling is accomplished by immersing the bottles in 
clean, cold water. With other types the bottles are heated by im- 
mersing in vats containing hot water. 




Fig. 12. — Front view of in-the-bottle pasteurizer, showing the fine sprays of hot water 

used in heating the milk. 



22 BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 

Some of the advantages of pasteurizing in the bottle are : 

1. Operation is comparatively simple. 

2. For a small dealer the first cost is comparatively small. 

3. The apparatus is durable. 

4. There is little chance of recontamination of the milk after pasteuriza- 
tion, provided water-tight caps are used and bottles do not have to be 
recapped. 

5. The bottle as well as the milk is heated. 

6. In some cases small plants can save space by its use, as the pasteur- 
zer serves also as a cold-storage room. 

7. No apparatus, pumps, or pipes to clean. 

Some of the disadvantages of in-the-bottle pasteurization are : 

1. The system is rather slow for a large commercial plant. For a small 
plant, however, this objection may not be serious. 

2. Cf)nsiderable extra steam and refrigeration are required, as it is 
necessary to heat and cool the bottles, caps, and cases, in addition to 
the milk. 

3. During the heating process the milk will expand in the bottle, so that 
miless a bottle of extra capacity or a special and more expensive cap is 
used, many of the bottles will have to be recapped after cooling, because 
the expansion of the milk will force the cap out. It is advisable to use 
a. bottle of extra capacity, since recapping, besides causing considerable 
trouble, may contaminate the milk. Whei-e extra-sized bottles are used 
they contain full measure of milk, but there is some empty space between 
the top surface of the milk and the cap to allow for expansion during heat- 
ing. Such bottles do not appear full when delivered and thus may cause 
some complaint among customers. 

SYSTEMS OF PASTEURIZING USED. 

Various systems of pasteurizing used at 237 plants are shown in 
Table 5. It will be noted that the vat and in-the-bottle systems are 
more common with the smaller plants, while film and tubular types 
are more common with the medium-sized and large plants. Seventy- 
five of the 237 plants were using temperature recorders, and 67 plants 
were using temperature regulators. 

One of the important factors in a pasteurization system is an even 
flow of milk into the pasteurizer and also from the heater to the 
holder. If the flow is constant throughout the apparatus more ac- 
curate results will be obtained. At some plants where a gravity sys- 
tem is used a float valve is attached to the apparatus. This valve 
will allow only a certain quantity of milk to flow to the pasteurizer 
per hour. A similar valve placed at the outlet of the pasteurizer will 
allow the same quantity to go to the holder per hour. In this way 
more nearly uniform results are obtained in heating and holding. 



MILK-PLANT EQUIPMENT. 23 

Table 5. — Types of pasteurizers used at 237 plants of various sizes. 



Milk handled ,t„,. 
daily. ^^*- 


Tubular. 


Film or 
drum. 


Kettle. 


In the 
bottle. 


In the 
can.< 


Total 
all types. 


Number 
of these 

plants 

using the 

flash 

system. 


Gallons. 
Up to 100 


14 
27 

26 
3 24 






1 
2 


4 
5 


3 


12 
15 

38 
52 
48 
40 
18 
5 
9 




101 to 250 




1 
2 
8 

12 
9 

12 


1 


251 to 500 

501 to 1,000 


1 
9 
12 
12 
4 
3 
3 


6 2 
10 1 


1 


4 
4 


1,001 to 2,000 


14 

8 
2 


7 
10 


3 

1 




3 


2,001 to 4, 000... 




2 


4,001 to 6,000 




1 


6,001 to 10,000 

Over 10,000 


2 

1 










4 


1 
















Total 


SS 


44 


48 


37 


16 


4 


237 









1 Two of these were starter cans. 

2 One was the "spray" vat system. 

3 Two were the "spray" vat system. 

* Cans set in vat of water which is heated with live steam. 

TEMPERATURE REGULATOR. 

Automatic temperature control is essential to the pasteurizing 
plant. It is very "difficult and often impossible to control the tem- 
perature by means of hand valves, but there are many automatic 
devices on the market which control the temperature with great 
accuracy. In a plant without an automatic control a large propor- 
tion of a man's time must be spent at the steam valve if the tem- 
perature is to be kept within proper limits. During the process of 
l^asteurization one man has to spend the greater part of his time 
there, and even then it is very difficult to prevent frequent varia- 
tions in temperature. Not only may the cream line be injured by 
such irregular temperatures, but the results, both from bacteriologi- 
cal and chemical points of view, are unsatisfactory. 

RECORDING THERMOMETER. 

The recording thermometer is another appliance that should be 
used in all plants where milk is pasteurized. By means of this de- 
vice a record of the temperatures of the milk during the whole 
day's run is made. Each day the superintendent has a report which 
shows the temperature to which the milk is heated at any period 
of the process and also, within certain limits, how long it was held 
at the pasteurizing temperature. Thus, although not necessarily 
present himself, he can keep a reliable check on the operator. These 
records can also be shown to complaining customers or to health 
officials as evidence as to how the milk was pasteurized. 

Recording thermometers must be tested after being set up and 
checked with an accurate hand thermometer. They may get out 
of adjustment and should be checked up frequently. 



24 BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 




Fig. 13. — Temperature controller for heating milk to desired temperature iu pasteur- 
ization. 



There should be a supply tank between the milk coolers and the 
fillers. If anything happens to the fillers it will not be necessary 
then to shut down the pasteurizer. The supply tank will equalize 
the flow Qf milk from the pasteurizers to the fillers. 



MILK-PLANT EQUIPMENT. 



25 



BOTTLE FILLERS AND CAPPERS. 

In order to i^ut the milk into bottles for the trade, bottle fillers 
and cappers are required. There are many types. At some small 
plants the bottles are filled by hand or by the use of a dipper. This 
is very unsatisfactory even for a small plant, both because of the 
chance of contamination and the danger that the milk is not uni- 
form in butterfat content. Hand filling is also slow and tedious. 

Bottle fillers used by the smaller dealers consist of a tank mounted 
on a metal framework and containing valves either at one or both 
ends of the tank. The smaller ones have four valves at one end, 
while the next larger-sized machines have four valves at one end 
and five at the other. Quarts may be filled at one end while pints 
are being filled at the other end. With the next size of filler a full 
case of bottles is filled at one operation (figs. 15 and 16). When the 
bottles are full the case goes on to be capped either by hand or 




Fig. 14. — Chart for temperature recorder, showing temperatures and time of heating, hold- 
ing, and cooling eight different batches of milk. In-the-bottle system of pasteurization 
was used. 



26 



BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 




Fig. 15. — Filling bottles by maoliine of lever type and capping by hand. 

machine. Some fillers of this type have 12 valves at one end o-f the 
tank and 20 at the other, so that a case of quarts and pints can be 
filled as desired, and both can be filled at the same time by having 
a man to operate each end of the machine. The capping machines 
cap one row of bottles or a whole case, depending on the type of 
machine, at one stroke of the lever. 



AUTOMATIC SINGLE-BOTTLE AND ROW FILLERS. 

So-called rotary fillers and cappers (fig. IT) have been introduced 
in recent years and are used extensively. This filler consists of a 
circular tank with valves similar to those of the other types of 
fillers. The bottles are removed from the cases and placed on a 
revolving carrier, which brings them under the valves of the tank. 
Each bottle is automatically raised as it comes under the valve and 
the milk flows into it. When the bottle has traveled the full revolu- 
tion of the tank it is automatically lowered and the valve closes. 
By revolving a full revolution the bottles have ample time to be 
filled. The bottles are then carried to the capper, which caps them 
automatically. With large machines of this type one man is required 
to take bottles out of the cases and feed them to tlie filler while 
another man removes the filled and capped bottles from the machine 
and returns them to the cases. There are several sizes of these 



MILK-PLANT EQUIPMENT. 



27 



machines, and the tanks have from 8 to 12 or more valves. From 
24 to 72 or more bottles can be filled and capped per minute, depend- 
ing on the size of the machine. 

With the so-called roAV fillers the bottles are also taken from the 
case and placed under the valves by hand. They are partially filled 
under the first set of valves and move on to have the filling com- 
pleted by a series of additional valves. After capping, Avhich is done 
by machine, full bottles are removed and replaced by hand in the 
case. 

Some of the advantages of these types of fillers are : 

1. Simplicity. 

2. The bottles can he inspected when filled before being returned to the 
cases. 

3. The capacity of the plant can be increased gradually by adding more 
units of the same capacity without decreased economy in the use of labor. 

4. Small floor space is required. 

AUTOMATIC CASE FILLERS AND CAPPERS. 

Some of the large plants have automatic power fillers and cappers 
(fig. 18). Usually the fillers and cappers are operated by electric 
power, and in some cases the valves are operated by hydraulic 
pumps. With these machines a full case of bottles is filled and 
capped automatically. All the operator does is to feed the cases of 




Fig. 16. — Machine filling and capping bottles. 



28 BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 




Fig. 17. — Rotai'y flllin.s? and capping machine. 

empty bottles to the machine and take them away filled and capped. 
From 5 to 10 cases a minute can be filled and capped with these 




Fig, 18. — Type of automatic filling and capping machine. 

machines. They are more expensive, and some types are difficult 
to operate. Being more complicated they require careful attention 
in order to keep them in good working order. 



MILK-PLANT EQUIPMENT. 
BOTTLE WASHERS. 



29 



There are several types of bottle washers. At some small plants 
the bottles are simply swabbed out with a hand brush and then 
rinsed. The next advance over this process is the washing of bottles 




Fii:. 111. rurl)ioe-bruRb bottle washer. Bottles are rinsed by sprays of boiling water 
forced into them by pump. 




Fig. 20. — An automatic bottle washei. As high as 2,000 bottles per man per hour were 
washed with this type of machine. 



30 



BULLETIN 8^10, U. S. DEPARTMENT OF AGKIGULTUEE. 




Fig. 21. — \Yashing, steaming, and drying cans. 



on a revolving brush. The brush is made to revolve by means of a 
steam turbine, engine, or motor, and in a few cases a water turbine. 
After the bottles are washed they are returned to the case and rinsed 
and steamed. With some machines this is done by means of a two- 
way valve which first forces hot water into the bottles and then 
live steam. Other machines are provided with a pump which pumps 
water at a high temperature into the bottles. The bottles should be 
inverted in the cases after washing ; otherwise the water on the cases 
will drip into the bottles below when the cases are stacked. 

At most large plants automatic power washers are used. There are 
several different types of these power washers, but the most common 
one consists of a series of tanks containing water at various tempera- 
tures. The first tank contains a solution of alkali or washing 
powder. By means of powerful pumps these solutions and water are 
forced through jets into the bottles in the cases. The first solution is 
warm, and the solution or water in each succeeding tank is hotter than 
in the one before. The last water to be forced into the bottles is 
almost at the boiling point, and the bottles may then receive a spray 
of steam. Temperatures observed in various tanks at four plants are 
shown in Table 6. One man usually feeds the cases of bottles into 
this machine while another man takes them out at the other end. 
Very dirty bottles can not be cleaned by such machines, but should be 
washed first with a brush machine and then sent through the auto- 
matic machine for rinsine: and steaming. 



MILK-PLANT EQUIPMENT. 



31 



Table 6. — Temperatures observed in various tanks of automatic jet hottle 

washers. 





Plant No. 


Tank 1. 


Tank 2. 


Tank 3. 


Tank 4. 


1 


♦ 


op 

90 
100 
110 

90 


'F. 
120 
120 
150 
140 


"F. 
100 
140 

ISO 
180 


"F. 
200 


2 


170 


3 




4 . 









It is very important that the proper temperature be maintained in 
the various tanks. The temperature in the first tank must not be so 
high as to break the bottles, and it should be increased in each tank 
so that the final tank will be kept at a temperature near the boiling 
point. Care must also be taken to have the proper solutions in the 
various tanks. The first tank of large machines contains a strong 
alkali solution, the second a milder solution, and the remaining tanks 
rinsing water. 

CAN WASHERS. 

Can washers are of various types. Some of them are brush ma- 
chines while others operate on the same principle as the automatic 
bottle washers described, that is, by forcing solutions of washing 
powder, hot water, and steam into the cans. In order to facilitate 
drying, some of these machines also blow a blast of air into the can 
after steaming. 




Fig. 22. — Roller conveyers as labor-saving devices. 



32 BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 

Dealers should give considerable attention to the question of wash- 
ing the cans. If they are allowed to go back unwashed it is a very 
difficult if not an impossible task for the farmer, with his limited 
facilities, to clean them properly. It does not matter what method 
is used, so long as the cans are well rinsed, sterilized, and dried. The 
drying of the cans is an important factor. It not only leaves the can 
in a more sanitary condition but preserves its life by preventing 
rust. The cover should also be thoroughly cleaned and sterilized, but 
should not be put on the can until the latter is dry. When the covers 
are not put back on the cans immediately the cans should be kept 
in a clean place where there is no dust or contamination. The covers 
should be placed tightly on the cans before they are returned. 

The milk dealer must have a machine that will do rapid work, 
but the main result to be obtained is a clean, sterile, and dry can, 
regardless of the method used. Many of the machines on the market 
do not steam the cans long enough. Some dealers get good results 
by washing the can in a sink with a hard brush, then rinsing and 
IDlacing it OA^er a jet which blows live steam into it. If the steam is 
allowed to go into the can long enough the can will dry in a few 
moments after being removed. Each can should receive live steam 
for at least 45 seconds. 

LABOR-SAVING DEVICES. 

Considerable labor can often be saved by the use of labor-saving 
devices, such as elevators and conveyers. Some conveyers operate 
by gravity, while with others power is used. This equipment is 
expensive, and, of course, only such quantity should be purchased as 
can be used economically. Many steps and much labor, however, 
can be saved by the proper use of these devices. A conveyer to run 
cans of milk from the receiving platform to the dump tanks often 
saves much labor. A conveyer from the clean-bottle storage room 
through the bottle-filling room to the cold-storage room will, in 
many plants, save at least one man, while a conveyer from the cold- 
storage room to the loading platform will greatly expedite the load- 
ing of the delivery wagons and save labor at many plants. The same 
conveyer can often be used for two purposes at the same plant ; the 
track that is used to convey the milk into the storage room during 
the day can be used at night in loading the delivery wagons. At 
some plants a conveyer is used to convey the cases of empty bottles 
from the receiving platform to the bottle-washing room, thus pre- 
venting congestion on this platform and expediting the work. The 
economy of these labor-saving devices is shown in Tables 1, 2, 3, 
and 4 in Department Bulletin 849, City Milk Plants. 



MILK-PLANT EQUIPMENT. 



33 




Fig. 23. — Compression typo of refrigerating macliinc. 



POWER PLANT. 



The power plant should be in a separate building if possible. If 
this is impracticable, it is well to have it in the basement of the 
plant. If the power plant must be adjacent to the rest of the plant, 



34 BULLETIN 890, U. S. DEPAKTMENT OF AGRICULTURE. 

it is important that the boiler room be far enough away and so 
inclosed that dirt, soot, and fumes will not reach the milk-handling 
rooms. The power plant should be of ample capacity, so that none 
of the equipment or apparatus need be forced. It may be advisable 
for large plants to have two refrigerating machines and two boilers. 
Considerable power may be saved at certain times of the year by 
operating only one of the machines when the full capacity of refrig- 
eration is not needed. By having two boilers, one can be cleaned or 
repaired without shutting down the plant. 

STEAM OR ELECTRIC POWER. 

Whether a steam engine or electric motors should be used will 
depend largely upon the costs of current and coal. The use of motors 
has several advantages, and direct-connected motors for each ma- 
chine are advisable whercA^er possible, although where several ma- 
chines are grouped together less power will be required if only one 
motor is used to run the shafting for all the machines. At large 
plants electric current to run the motors can often be generated for 
much less than it can be bought. Some of the advantages of 
motors are : 

1. Simplicity of operation. 

2. CIeanlines.s. 

3. Power Is used only when machine is operated. 

4. Small space required. 

5. Power used in operating a machine may be determined accurately at 
any time. 

6. Obviates insanitary hangers, shafting, and pulleys. 

Some of the advantages of the use of steam engines in milk 
plants are : 

1. The exliaust steam can be utilized. 

2. The source of power is under the control of the milk plant. 

3. A steam boiler nmst be used anyway to sui)ply steam for hot watei-, 
pasteurizing, sterilizing, and for heating the building. 

Whatever power is used it is well to have an auxiliary system, so 
that if anything happens to one system the plant will not have to 
be shut down. A plant using motor power should have an engine for 
an emergency, while a plant using engine power should either have 
an extra engine or some electric motors installed. 

ARTIFICIAL REFRIGERATION. 

Most large plants use artificial refrigeration, but there are 
many smaller ones that still depend upon ice. Individual condi- 
tions will determine which will be more economical to use. 

The methods of producing artificial refrigeration are familiar 
to most milk dealers. They are fully described in United States De- 
partment of Agriculture Bulletin 98. 



MILK-PLANT EQUIPMENT. 



35 



In some plants the refrigeration medium is expanded directly into 
the cooling coils, while in others brine is used. (The ])rine is kept 
cold by passing the ammonia pipes through it.) The brine is 
pumped into the cooling coils, or it may remain in the tank, thus 
keeping the room cool a long time after the refrigerating machine 
has been stopped. Both the direct-expansion ammonia system and 
the brine system have their advantages. In large plants where re- 
frigeration is needed continuously for cooling the milk and the cold- 
storage room the direct-expansion system is more economical than 
the brine storage. In small plants where the cooling is done in a 
comparatively short time it is more economical to use the brine- 
storage system of refrigeration, owing to the fact that a smaller 
compressor may be used and refrigeration for use in cooling the 
milk and storage room may be stored in a large quantity of brine 
and held for quick action when needed. However, when the larger 
part of the day is consumed in pasteurizing, so that uniform re- 
frigeration is required, the direct-expansion system is often used. 
In order that the refrigerating machine need not be run contin- 
uously most plants use brine tanks in the cold room, so that the 
room can be kept cold for a considerable time after the machine is 
shut down. 

Table 7. — Systems of cooUny viilk at 8'i milk plants. 



Quantity of milk handled daily. 



Number of 
plants using 

direct- 
expansion 
ammonia. 



250 or less gallons 

251 to 500 gallons 

501 to 1,000 gaUons... 
1,001 to 2,000 gallons.. 
2,001 to 5,000 gallons.. 
5,001 to 10,000 gallons. 
Over 10,000 gallons.. . 



Total. 



Number of 

plants using 

the brine- 

circuJat ing 

system. 



Number of 

plants using 
ice water. 



Total. 



There are many advantages in the use of brine over direct expan- 
sion alone in a milk plant, some of which are : 

1. The system is more elastic ; the Virine can he stored up for cooling 
after the refrigerating mncliine has heen shut down or in case of a 
breakdown. 

2. There is less danger of freezing the milk on the cooling pipes with the 
• trine system of cooling. 

3. Pipes need not be so strong as those required for the direct-expansion 
system of cooling milk. 

4. There is less danger of leaks in tlie pipes than if direct expansion is 
used, and therefore less danger of tainting the milk. 

5. For small or medium-sized plants the machine would have to run 
longer if direct expansion only were used, because with the brine system 
the machine may store up refrigeration in the brine to last for 10 or 12 
hours, while only 2 or 3 hours are required for cooling the milk. 



36 BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 

The direct-expansion system is the most economical at phints where 
it is necessary to run the machine continuously, as less refrigeration 
will be lost if it goes directly to the cooler than when it goes through 
the secondary brine medium. 

Many plants use a combination of the two systems. Direct- 
expansion coils are used in the cold room and brine is circulated from 
a tank, usually in the cold room, through the milk cooler. 

Whether direct expansion or brine is used in cooling the millc, it 
is usually more economical to use water in the first few coils of the 
cooler, as refrigeration is thus saved. In some plants, instead of 
using brine or direct expansion for cooling the milk, refrigerated 
water is used; that is, water for cooling is cooled by means of brine 
coils or direct-expansion coils. In this way the temperature of the 
cooling medium is accurately regulated and extreme temperatures are 
not required. 

Under ordinary circumstances 'artificial refrigeration is cheaper 
than the use of ice for medium-sized or large plants. With careful 
operation there is very little waste of refi'igeration, the original 
cost of machinery and the labor and power being the chief items of 
expense. In a medium-sized or small plant, however, it is often a per- 
plexing problem to the dealer whether to install an artificial refrig- 
erating plant or to depend upon ice. In deciding this question it 
is necessary to consider such factors as the price of ice, quantity 
required each day, labor of handling, the disadvantages incident to 
its use, and the certainty of a supply of ice. Then come the ques- 
tions of size, initial cost, and the cost of operation of a refrigerating 
plant which would accomplish the same result. 

In some cases it may be necessary to increase the size of the boiler 
and of the engine, which should, of course, be large enough to run 
the compressor while the pasteurizer, bottle washer, and other ma- 
chinery are being operated. If electric power is to be used, the size 
of the boiler need not be considered. 

In comparing the cost of artificial refrigeration with that of ice it 
should be remembered that in many cases the former is of greater 
value than can be estimated, on account of the better results ol)tained, 
for when ice is used it is often difficult to maintain a temperature low 
enough to keep the milk in proper condition. 

Some of the disadvantages of the use of ice are the following : 

• 

1. Cost of ice is often high. 

2. Extra worlv required in handling. , 

3. Mold and slop incident to its use. 

4. Moist atmosphere caused by its use. 

.^). Difficulty of obtaining temperature below 50° F. in storage room. 
r>. Waste caused by melting in handling. 
7. Ice not always obtainable. 



MILK-PLANT EQUIPMENT. 37 

A supply of natural ice is uncertain, depending on weather condi- 
tions; some years there is a shortage, and in the South, of course, 
natural ice can not be obtained. Aside from the possibility of acci- 
dent a refrigerating machine can be depended upon to supply the 
requisite amount of refrigeration at all times. ' Furthermore, it re- 
sults in cool, dry air in the storeroom, produces lower temperatures 
than ice, and permits more accurate control of temperature. Where 
artificial refrigeration is used less ice is required on the delivery 
wagons, since the original temperature of the milk is lower. Many 
plants find it profitable to manufacture ice for sale as well as for 
their own use. This requires very little extra labor and overhead, 
and yields an additional cash income. 

USE OF EXHAUST STEAM. 

If exhaust steam from the engine is allowed to escape unused a 
valuable by-product is wasted and the coal bill is correspondingly 
high. Exhaust steam can be used successfully for pasteurizing milk 
or cream, heating boiler-feed water and water for washing purposes, 
and for heating the building. By using an exhaust-steam water 
heater an abundant supply of water at a temperature of about 200° 
F. is made available. 

If a plant has an engine and in pasteurizing uses the exhaust 
steam instead of live steam direct from the boiler, the cost of the 
steam for heating the milk and pasteurizing is practically eliminated. 
Generally the exhaust from the engine will furnish all the necessary 
heat. Therefore, in figuring the size of the boiler required, at a 
plant using an engine to run the pasteurizers, bottle washers, and 
other apparatus required in the ordinary retail milk plant, the 
amount of steam to I'un the engine only need be considered, if the 
exhaust steam is utilized for pasteurizing. 

To heat 300 gallons of milk from 60° to 145° F. requires about 30 
pounds of coal, and with that quantity of milk handled daily an ex- 
haust-steam lieater would effect an annual saving of more than 5 
tons of coal. In case the water from the heater is too hot for the type 
of pasteurizer used, the temperature should be regulated automati- 
cally. 

The equipment for utilizing the heat in the exhaust steam m a 
medium-sized plant is simple and inexpensive.^ Information in re- 
gard to these heaters can be obtained by writing to the Dairy Divi- 
sion, United States Department of Agriculture, Washington, D. C. 

The water used in cooling the milk should be saved and not run 
down the sewer, as is done in many plants. By piping it back to the 
heater or to a tank, not only would the water itself be saved but also 
a considerable quantity of coal. Much water in a milk plant can be 

^ See I'liitcd States Department of Agriculture Bulletin 747. 



38 



BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 



used many times in order to get the most use out of both the water 
and the heat it contains. 

COST OF PLANT EQUIPMENT. 

Investments in phmt equipment at 125 plants of various sizes are 
shown in Table 8. While there is considerable variation in the in- 
vestment at i^lants of the same group, some idea can be obtained of 
the amount of money that is invested in plant equipment. The 
plants are in various parts of the country. 

Table 8. — Investments in plant equipment and machinery for plants of various 

sizes.^ 



Quantity of milk handled daily. 



100 or less gallons 

101 to 250 gallons 

251 to 500 gallons 

501 to 1,000 callons. . 
1,001 to 1,500 gallons. 
1,501 to 2,000 gallons. 
2,001 to 3,000 gallons. 
3,001 to 5,000 gallons. 
5,001 to 10,000 gallons 
Over 10,000 gallons. . 



Number 
of plants. 



Average 
niunber 
of gallons 
handled 
daily. 



Gallons. 

71 

1S9 

399 

782 

1,290 

1,822 

2,597 

4,094 

8, 275 

17,298 



Average 
invest- 
ment in 
plant 
equip- 
ment. 



^'ariation. 



$932 

1,983 

4,864 

9,177 

1(5,338 

20,972 

29, 2(iS 

45, 200 

123, SOO 

108,019 



$500- 1,311 
400- 5,000 
1,181- 15,700 
3,200- 20,000 
4,000-33,008 
7,500- m,ooo 
10,000- 47,850 
10,737-100,000 
30,000-205,000 
82,000-537,000 



125 2,112 $24,475 400-537,000 $1,159 $212-5,000 



Average 
equip- 
ment in- 
vestment 
per 100 
gallons 
handled 
dailv. 



$1,308 
1,018 
1,219 
1,172 
1,201 
1,480 
1,127 
1,104 
1,496 
971 



Varia- 
tion. 



$625-1,714 
212-2,-500 
318-3,140 
400-2,500 
333-3, 1X2 
409-5, 000 
200-2, 175 
268-2,000 
558-2, (-50 
639-1,344 



1 Based on 1916 priees. 

LISTS OF EQUIPMENT REQUIRED FOR VARIOUS-SIZED PLANTS. 

On the following pages are lists of the principal equipment re- 
quired for plants of various sizes and the approximate total cost. 
These figures on cost are given only as a guide for comparison. 
The cost of the equipment will depend a great deal on the type of 
machinery selected, kind of contract made, and the character of 
the business. As prices are continually changing only approxima- 
tions can be made as to the cost of equipment. The number of milk 
cans and bottle cases required will depend upon the individual 
])lant, but in these lists are given the approximate quantity that 
would be needed. 



I'rincipul c(juipvicnt for plant of 100 i/nllnns' caixirltiJ. 

(capacity 1,500 



1 platform scales. 

1 pasteurizer (100-gallon vat). 

1 temperature recorder. 

1 sanitary milk pump. 

1 sanitary piping and fittings. 

1 brine tank. 



1 brine pump. 

1 tubular cooler 

pounds an hour). 
1 bottle filler. 
1 turl)ine-brusb bottle washer 

tank, rinser, and steamer.- 



with 



MILK-PLANT EQUIPMENT. 



39 



1 can wash sink with steam jet. 

1 separator. 

1 cliurn. 

50 bottle cases. 

20 10-LMllon cans. 



1 3-horsepower motor. 
1 10-horsepower boiler. 
Shafting, belting, pnlleys, 
piping, pipe, fittings, etc. 
Chemical apparatus. 



hangers 



Estimated cost of the plant equipment, from $1,500 to $2,000. 

Principal equipment for a plant of from 300 to 500 gallons' capacity. 



1 platform scales. 

1 300-gallon pasteurizing vat. 

1 temperature recorder. 

1 tubular cooler (capacity 4,000 

pounds an hour. 
1 brine tank. 
1 brine pump. 
1 sanitary milk pump. 
Sanitary milk piping and fittings. 
1 bottle filler. 
1 bottle washer (turbine brush, rinser, 

and steamer). 
1 can rinser and steamer. 

Estimated cost, from $3,500 to $4,000. 



1 separator. 

1 churn and butterworker. 

60 10-gallon cans. ' 

150 milk-bottle cases. 

1 dozen case trucks. 

1 hand truck. 

1 5-horsepower motor. 

1 20-horsepower boiler. 

Belting, shafting, pulleys, hangers, 

piping, pipe fittings, etc. 
Steam and water hose with fittings. 
Chemical apparatus. 



Prinoipal equipment for a plant of from 500 to SOO f/allons' capacitif. 



1 2-valve dump and weigh can with 
strainer rack. 

1 platform scales. 

1 drip saver. 

1 200-gallon receiving vat with cover 
and coils. 

1 sanitary milk pump. 

Pasteurizing and cooling outfit, 3,000 
pounds an hour with automatic 
tenriierature control and recording 
thermometers. 

Sanitary piping and fittings. 

1 filler and capper. 

1 hydraulic bottle washer; 2 compart- 
ments, power feed. 

1 small wash sink with turbine brush. 

1 wash sink with can rinser, steamer, 
and dryer. 

1 separator. 

1 40-gallon cream vat. 

1 100-gallon .iacketed vat. 

1 churn and butterworker. 

1 butter printer, ladles, and packer. 

Estimated cost, from $8,000 to $10,000, 



1 starter can for buttermilk. 
100 10-gallon cans. 
250 milk-bottle cases. 

2 hand trucks. 
Conveyer track. 
1 5-ton ice machine. 
1 brine tank with piping. 
1 brine pump. 
1 12-horsepower engine. 
1 25-horsepower boiler with all neces- 
sary fittings and accessories. 

Belting, shafting, pulleys, hangers, 
piping, pipe fittings, etc. (If live 
steam were used for pasteurizing, 
the boiler capacity should be 
doubled.) 

1 special exhaust-steam water heater 
and storage tank (to supply hot 
water for pasteurizing and for wash- 
ing purposes). 

Chemical apparatus. 

Bacteriological apparatus. 



40 



BULLETIN 890, U. S. DEPARTMENT OF AGRICULTURE. 



Principal cquipiiioit for a phnit of froiii .1.000 to 1,500 (jalJons' rfipdcUy. 



1 2-valve dnnrii and \vei,iih can. 

1 platform scales. 

1 drip saver. 

1 sanitary milk pnnip. 

1 300-gallon receiving vat with cover 
and coil. 

Pasteurizing and cooling outfit vpitli 
automatic temperature control and 
recording thermometers (capacity 
4,000 pounds an hour). 

1 clarifier (4.,000 to 6,000 pounds an 
hour). 

Sanitary milk piping and fittings. 

1 supply tank to filler. 

1 filler and capper. 

1 small filler for buttermilk. 

1 hydraulic bottle washer ; 3 com- 
partments, power feed. 

1 small bottle washer with turbine 
brush. 

1 can washer, rinser, steamer, and 
drier. 

1 separator. 

1 .50-gallon creamr vnt. 

1 1.50-gallon jacketed vat. 

Estimated cost, from .$18,000 to .$2.5 



1 churn and butterworker. 

Butter printer, ladles, and packer. 

1 starter can. 

200 10-gallon cans. 

500 milk-bottle cases. 

Trucks or conveyer tracks. 

1 8-ton ice machine, with brine tank, 
piping, brine pump, etc. 

1 20-horsepower engine. 

Motors. 

1 40-horsepower boiler with all nec- 
essai-y fittings and accessories (al- 
lowing 3 hours to pasteurize and cool 
1,200 gallons milk). 

Shafting, pulleys, belting, hangers, 
piping, pipe fittings, valves, etc. (If 
live steam were iised for pasteuriz- 
ing, the boiler capacity would Imve 
to be increased.) 

1 special exhaust-steam water heater 
and storage tank to supply liot water 
for pasteurizing and for washing 
purposes. 

Chemical apparatus. 

Bacteriological apparatus. 

000. 



Principal equipment for a plant of from 2,500 to .',,000 (lalUm^' capacity. 



1 2-valve dump and weigh can. 

1 platform scales. 

1 drip saver. 

1 sanitary milk pump. 

1 300-gallon receiving tank with 
cover and coil. 

1 clarifier (8,000 pounds an hour ca- 
pacity). 

Pasteurizing and cooling outlit with 
automatic temperature regulator 
and recording thermometers (ca- 
pacity 6,000 pounds an hour). 

1 100-gallon vat pasteurizer. 

Sanitary milk piping and fittings. 

1 supply tank to filler. 

2 fillers and cappers. 

1 small filler for buttermilk, etc. 

1 hydraulic bottle washer (4 compart- 
ments, power feed). 

1 small bottle washer with turbine 
brush. 

1 can washer, rinser, steamer, and 
drier. 



1 forewarmer. 

1 separator. 

1 churn and butterworkei-. 

Butter printer, ladles, and packers. 

450 10-gallon cans. 

1,.500 milk-bottle cases. 

Trucks and conveyer track. 

1 starter can. 

Motors. 

1 300-gnllou ripener. 

1 .300-gallon cheese vat. 

2 drain racks. 

1 buttermilk machine. 

1 18-ton ice machine with brine tank, 
piping, and pump. 

1 60-liorsopower boiler, with all nec- 
essai-y accessories and fittings (al- 
lowing 3i to 4 hours to pasteurize 
and cool 2,500 gallons of milk). Ex- 
haust steam used. (If live steam 
were used for pasteurizing the boiler 
capacity would have to be in- 
creased.) 



MILK-PLANT EQUIPMENT. 



41 



iiec- 



1 40-liorsepower engine, with a 
essaiT fittings and accessories. 

Belting, sliaftlng, pulleys, hangers, 
piping, fittings, valves, etc. 



1 special SOO-gallon exhaust-steam 
hot-water heater and storage tank, 
to supply hot water for pasteurizing 
and for washing purposes. 
Chemical apparatus. 
Bacteriological apparatus. 
Estimated cost, from ,$30,000 to $40,000. 
PrinciiJal equipment of a plant of approxiimitcly 5,000 gallons' capacity. 



1 2- valve dump and weigh can. 
1 platform scales. 

1 drip saver. 

2 claritiers (12,000 pomids an liour 
combined capacity ) . 

1 to 3 jacketed storage tanks (2,500 
gallons each). 

1 SOO-gallon receiving vat, with cover 
and agitator. 

Pasteurizing an<l cooling equipment 
(10,000 pounds an hour) with au- 
tomatic temperature regulator and 
recording thermometers. 

1 small pasteurizer for cream. 

1 small tubular cooler. 

2 sanitary milk pumps. 
Sanitary milk piping and fittings. 
1 supply tank to fillers. 

3 fillers and cappers. 

1 small filler for buttermilk, etc. 

1 hydraulic bottle washer (."i compart- 
ments, power feed). 

1 small bottle washer with turbine 
brush. 

1 can washer, rinser, steamer, and 
drier. 

1 forewarmer. 

1 separator (capacity 8,000 pounds an 
hour). 

1 300-gallon jacketed vat. 

1 rotary pump for skim milk. 

1 churn and butterworker. 

Butter printer, ladles, and packers. 



90(J 10-gallon cans. 
2,500 bottle cases. 
Conveyer track. 
Trucks. 
1 starter can. 
1 300-gallon ripener. 
1 500-gallon standardizing and mixing 
vat. 

1 300-gallon cheese vat. 

2 drain racks. 

1 butternrilk machine. , 
1 homogenizer. 

1 30-ton ice machine with brine tank, 
piping, brine pump, etc. 

2 125-horsepower boilers (one in re- 
serve) with all necessary accessories 
and fittings. (5,000 gallons of milk 
to be pasteurized at the rate of 
10,000 pounds an hour, in from 4 to 
4i hours.) 

1 60-borsepower engine, or 70 horse- 
power motor, to run ice machine. 

1 25-horsepower engine (exhaust steam 
used for pasteurizing and to heat 
water for washing). 

Belting, 'shafting, pulleys, hangers, 
piping, pipe fittings, valves, etc. 

1 special exhaust-steam water lieatei- 
and storage tank to supply hot water 
for pasteurizing and for washing 
purposes. 

Chemical apparatus. 

Bacteriological apparatus. 



Estimated cost, from $60,000 to $70,000. 

Clieiniral apparatus for arerage-nized milk plant. 



1 Babcock milk tester from 6 to 12 

bottles — hand or steam operated. 
3 dozen milk-test bottles, 8 per cent. 

1 dozen cream-test bottles, 50 per cent. 

2 pipettes, 17.6 c. c. 

1 combined acid bottle and pipette. 

1 lactometer (Quevenne). 

1 burette, .50 c. c., graduated in tenths. 



1 burette holder. 

1 dozen beakers, 150 c. c. 

1 dropping bottle, 30 c. c. 

1 cream-test scale. 

1 pipette, 10 c. c. 

1 pipette, 25 c. c. 

i dozen skim-milk test bottles. 



Approximate total cost, from $45 to $65. 



42 



BULLETIN 890, U. S. DEPARTMENT OF AGEICULTUEE. 



Chemicals for cliemlcul inmlysis of milk and cream. 



Sulphuric acid, conmiercial, I gallon. 
Phenolphthaleiu, 1 per cent solution, 
100 c. c. 



Sodium hydroxid, tenth normal, 1 
liter. 



liartcriological apparwtus for tnilk plant. 



1 autoclave, medium size. 

1 dry-sterilizing oven, gas stove, and 
kitchen oven. 

1 incubator, 10 by 8 by 6 inches, in- 
side dimensions. 

1 balance, with weights to 5 liilos. 

100 1 c. c. pipettes, graduated iu tenths 
with an extra tenth above the 
mark. 

1 5 c. c. pipette. 

1 10 c. c. pipette. 

1 2.5 c. c. pipette. 

1 100 c. c. pipette. 

1 100 c. c. cylinder, graduated. 

1 500 c. c. cylinder, graduated. 

1 1,000 c. c. cylinder, graduated. 

2 dozen Erlenmyer flasks, 1,000 c. c. 
100 petri dishes, 100 by 10 m. m. 



4 dozen glass l)ottles, S ounces, pre- 
scription or French square. 

2 funnels, glass, 6-inch. 

1 double boiler, 4 gallon. 

1 thermometer (—10° to 100° C). 

1 thermometer (0° to 250° C. for dry 
sterilizer). 

1 dozen gla.ss stirring rods (assorted). 

2 petri-disli holders, sheet irou, 50 
dishes. 

2 pipette boxes. 



glass, 2* magnitications, 4 



1 readinj; 
inches. 
1 counting plate. 
1 tallying machine. 

1 gas stove, single burner. 

2 Bunsen burners. 

12 feet gas tubing, J inch. 
2 wax pencils, blue or red. 



Chemicals and accessories for hacieriohxjical examination. 



1 liter sodium hydroxid, tenth normal. 
1 liter sodium hydroxid, nornral. 
1 liter hydrochloric acid, tenth normal. 
1 liter hydrochloric acid, normal. 
Absorbent cotton. 



Nonabsorbent cotton. 
Canton flannel for filtering. 
Filter papers. 
Peptone. 



This bulletin and other department literature dealing with milk 
plants point out some of the more important economic and sanitary 
problems in the handling and distribution of milk. While all details 
can not be covered in these publications, they may serve to direct the 
attention of milk-plant operators or prospective operators to matters 
that might otherwise be overlooked. 



o 



